1. Field of the Invention
The present invention relates to a fluorescent lamp device and a method of fabricating a fluorescent lamp device, and more particularly, to a flat-type fluorescent lamp device and a method of fabricating a flat-type fluorescent lamp device.
2. Discussion of the Related Art
In general, cathode ray tube (CRT) devices have been commonly used for display monitors in televisions, measuring instruments, and information display terminals. However, the CRT devices are bulky in size and relatively heavy, and cannot satisfy demands for miniaturization and low weight. Accordingly, many substitutes have been developed for replacing the CRT devices, include liquid crystal display (LCD) devices that make use of electro-optical effects, plasma display panel (PDP) devices that use gas discharge, and electro-luminescence display (ELD) devices that make use of an electric field luminous effect. Among the many different display devices, the LCD devices are being developed to have low power consumption, thin profile, and lightweight for application in monitors for desktop and laptop computers.
Most LCD devices control light transmittance from ambient light to display an image. However, it is necessary to form an additional light source, such as a backlight unit, in an LCD panel. Generally, the backlight unit includes cylindrical fluorescent lamp devices that may be classified into two different types: direct-type devices and edge-type devices.
The direct-type backlight devices are suitable for large-sized LCD devices of 20 inches or more, wherein a plurality of lamps are arranged along one direction below a light-diffusion plate to directly illuminate an entire surface of the LCD panel with light. Accordingly, the direct-type backlight devices having large light efficiencies and are commonly used for the large-sized LCD devices that require high luminance. However, the direct-type backlight devices are problematic in that silhouettes of the fluorescent lamps may be reflected onto the LCD panel. Accordingly, since a predetermined interval must be maintained between the fluorescent lamps and the LCD panel, a thin profile LCD device that uses the direct-type backlight device is difficult to obtain.
In the edge-type backlight devices, the fluorescent lamps are formed at one side of a light-guiding plate, and light is dispersed on an entire surface of the LCD panel by the light-guiding plate. Accordingly, the edge-type backlight devices are generally applied to relatively small-sized LCD devices, such as monitors for laptop and desktop computers. However, the edge-type backlight devices provide low luminance since the fluorescent lamps are provided at one side of the light-guiding plate, and the light is transmitted through the light-guiding plate. In addition, advanced techniques for designing and fabricating the light-guiding plate are required to obtain uniform luminous intensity in the LCD devices that use the edge-type backlight devices.
FIG. 1 is a cross sectional view of a backlight device according to the related art. In FIG. 1, a backlight device is formed below an LCD panel that displays image data (i.e., a picture). The backlight device includes a main supporter 1, a lower cover 3, a lamp assembly 10, a light-guiding plate 5, lower and upper light-diffusion plates 6 and 9, and lower and upper prisms 7 and 8. The main supporter 1 supports respective components of the backlight device, and the lower cover 3 protects the main supporter 1. In addition, a fluorescent lamp is provided in the lamp assembly 10, and the light-guiding plate 5 transmits the light emitted from the fluorescent lamp to the LCD panel. Then, the lower and upper light-diffusion plates 6 and 9 are formed above the light-guiding plate 5 for diffusing the light incident on the light-guiding plate 5. The lower and upper prisms 7 and 8 condense the light diffused between the lower and upper light-diffusion plates 6 and 9, and transmit the condensed light to the LCD panel.
FIG. 2 is a perspective view of a backlight device according to the related art. In FIG. 2, a high-pressure lamp wire 13a, which is connected to a connector 16, and a low-pressure lamp wire 13b are respectively inserted into a high-pressure lamp holder 12a and a low-pressure lamp holder 12b. The respective lamp wires 13a and 13b are soldered, and the lamp holders 12a and 12b cover the soldering portions in the respective lamp wires 13a and 13b. Then, the lamp wires 13a and 13b are mounted in a lamp housing.
The lamp assembly is then assembled into the main supporter 1, and the lower cover 3 is assembled into the main supporter 1 to prevent the light incident portion of the main supporter 1 of the lamp assembly from being damaged due to external impact. Next, a reflecting plate 4 is mounted into an inner bottom of the main supporter 1, and the light-guiding plate 5 is mounted into the lamp housing 15 so that is has a uniform gap size and flatness. Subsequently, the lower light-diffusion plate 6, the lower prism 7, the upper prism 8 and the upper light-diffusion plate 9 are sequentially formed on the light-guiding plate 5.
When applying power to the fluorescent lamp by connecting the connector to a power supply, a glow discharge is generated within the fluorescent lamp, thereby emitting light. The light is incident on the light-guiding plate 5, and the incident light is reflected and scattered by printed dots on a lower surface of the light-guiding plate 5. The reflected and scattered light is condensed at a vertical direction by passing through the prism, and the condensed light is transmitted through the lower and upper light-diffusion plates 6 and 9, whereby the light is obliquely scattered. Accordingly, a rear portion of the LCD panel is irradiated with the light passing through the light-diffusion plate, and the reflecting plate 4 reflects the light that is not reflected or scattered by the printed dots of the light-guiding plate 5 to an upper direction.
However, the backlight device has the following disadvantages. The cylindrical fluorescent lamps in the backlight device are used as the light source and are formed at one side of the LCD device. Accordingly, it is difficult to obtain a uniform luminance across an entire surface of the LCD panel. In an attempt to obtain uniform luminance on the LCD panel with the backlight device, the light-guiding plate includes printed dots that are used for guiding the incident light to the upper direction. However, it is difficult to control the surface state of the light-guiding plate and the printed dots of the light-guiding plate. Thus, additional components are required that increase fabrication processing steps, thereby decreasing yield due to failures (i.e., bending or inaccurate sizing) of the light-guiding plate.
In addition, thermal expansion coefficients of the diffusion sheets are different from that of the components of the backlight device, thereby generating a ripple effect. For example, the light guiding plate has a higher hygroscopic property as compared with the main supporter, so that the size of the light-guiding plate may be easily changed. Thus, in case of the notebook computer having the backlight device, noise may be generated whenever the notebook computer is open or folded close.
Furthermore, it is hard to automate the fabrication process of the backlight device since it is important to prevent deposition of foreign particles within the backlight device, and to prevent scratches from being generating between the light-guiding plate and the diffusion sheets. Accordingly, manufacturing quality deteriorates and the yield decreases, and manufacturing costs increase.